minDistance.swift

func getMinDistanceBetweenRectangles(a: CGRect, b: CGRect) -> CGFloat {
    let deltaX = b.origin.x - a.origin.x
    let deltaY = b.origin.y - a.origin.y
    let delta = abs(deltaX) > abs(deltaY) ? deltaX : deltaY
    
    var distance: CGFloat = 0
    
    switch (delta >= 0, delta == deltaX) {
    case (true, true)   : distance = b.origin.x - (a.origin.x + a.width)
    case (true, false)  : distance = b.origin.y - (a.origin.y + a.height)
    case (false, true)  : distance = a.origin.x - (b.origin.x + b.width)
    case (false, false) : distance = a.origin.y - (b.origin.y + b.height)
    default: println("error")
    }
    
    return distance
}